For electronic control units to be mounted on vehicles, electric actuators such as motors and solenoids for converting electric signals into mechanical motions and hydraulic pressure are widely used as various objects to be controlled are electronically controlled. To drive these electric actuators, a load drive apparatus including a drive circuit including a semiconductor chip is used.
In the semiconductor chip of these load drive apparatuses, DTI that is one of insulation separation methods is used for the purpose of blocking noises and maintaining a potential difference when the drive circuit is integrated in the semiconductor chip.
As a background art in this technical field, there is a technique such as PTL 1. PTL 1 discloses a semiconductor device including a semiconductor substrate having a trench on a main surface thereof and an element formed on the main surface of the semiconductor substrate and having a conductive portion, the trench being formed so as to surround the element in plan view, the semiconductor device further including an insulating film formed on the element and in the trench so that the insulating film covers over the element and forms a hollow in the trench, the insulating film having a hole reaching the conductive portion.
In addition, PTL 2 discloses a semiconductor device including a semiconductor substrate having a structure in which a supporting substrate, a buried insulating film, and a semiconductor layer are stacked in this order and an element formed on a main surface of the semiconductor layer and having a conductive portion, the semiconductor device including a trench formed in the semiconductor layer so that the trench surrounds the element in plan view and reaches the buried insulating film from the main surface of the semiconductor layer, the semiconductor device further including a first insulating film formed on the element so that the first insulating film covers over the element and forms a hollow in the trench, the first insulating film having a hole formed to reach a conductive portion.
PTL 1 is a technique relating to a structure in which DTI is provided on an ordinary silicon substrate or a so-called bulk substrate, and PTL 2 is a technique relating to a structure in which the DTI is provided on a silicon on insulator (hereinafter referred to as SOI)
In addition, as an example of the load drive apparatus, there is a motor drive circuit as illustrated in FIG. 9. The motor drive circuit in FIG. 9 includes an inverter circuit INV including an FETH and an FETL that are filed effect transistors (FETs) that drive a motor, and a pre-driver circuit PDRV including a semiconductor chip 1.
In the semiconductor chip 1, input signals INH and INL are gone through a logic circuit LOGIC, a high-side driver circuit DRVH, and a high-side driver circuit DRVL, and a load drive output unit 3H that has OUTH as an output and a low-side load drive output unit 3L that has an OUTL as an output are driven, using gate signals GATEH0, GATEH1, GATEL0, and GATEL1. Here, the load drive output units 3H and 3L each includes a metal oxide semiconductor field effect transistors (hereinafter referred to as MOSFET) such as a laterally diffused MOS (LDMOS).